The present invention relates to communications and position location systems and specifically to a communications and position location system that may utilize laser light strings or normal laser light propagation.
Global positioning system (GPS) navigational and position location systems are often used by military and civilian naval, ground, and airborne vehicles for navigation. GPS systems can experience blackout areas or regions when line-of-site (LOS) is broken with the satellites due to signal blockage. For example GPS systems often experience loss of signal when they are operated in dense urban environments next to large buildings (e.g., urban canyon). Additionally recent attempts at augmenting GPS for this coverage deficiency has had mixed success and has not resulted in a low-cost widespread solution.
Communications systems operating in the VHF/UHF and higher frequency bands have LOS problems similar to GPS. Vehicles operating in a city or in rugged or mountainous terrain have difficulty communicating due to signal link-loss and blockage. Furthermore, there are few technical options for delivering high-speed data, video, and position location Information from a mobile unit or a large number of mobile units. For example, mobile units may include emergency response vehicles requiring broadband transmission of video from an emergency scene back to an emergency operations center. Rough terrain, line-of sight, ground network infrastructure and antenna technical challenges generally force or limit options having lower or unsatisfactory bit rate solutions. There are many solutions for providing high-speed data to a mobile unit. However most high data rate (broadcast) data channels options for mobile units with antenna height disadvantages do not work well for transmissions from the mobile units.
Laser diode technology has advanced in recent years with the development of low cost direct emission devices. These direct emission devices offer high-speed modulation capabilities for laser data communications systems. These state of the art laser diodes are available in several power levels and wavelengths including green, blue, and blue violet.
Laser communications systems known in the art provide end-to-end or point-to-point systems where a laser transmitter must be pointed directly at a laser receiver to establish communications. As with some radio communications systems, these laser communications systems are not useable in rough terrain or urban canyon situations.
There is a need for a position location and communications system that not only is less susceptible to blackout prone and high loss areas, but has wide bandwidth for high-speed data communications and is inherently low cost.